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Description
DIAMETER Ø25 mm
LENGTH 250 mm
INSERT TNMG 1604rr
ANGLE κr 60°
Technical specifications of the S25 MT-NR-16 boring bar
| Technical data | |
|---|---|
| ISO designation | S25 MT-NR-16 |
| Shank diameter (d) | Ø25 mm |
| Effective height (h) | 23 mm |
| Overall length (L) | 250 mm |
| Functional overhang (f) | 18 mm |
| Min. bore diameter (D_min) | Ø32 mm |
| Entering angle (κr) | 60° |
| Clearance angle | 0° (negative) |
| Clamping system | ISO — combination (M) |
| Insert type | TNMG 1604rr |
| Cutting direction | R — right-hand (L version available) |
| Shank material | Steel (S) |
| Manufacturer | Smoxh |
S25 MT-NR-16 boring bar – for internal turning of bores
Internal turning tool for machining bores from Ø32 mm
Boring bar S25 MT-NR-16 is an indexable boring bar designed for longitudinal turning and roughing and medium machining of bores with diameters from 32 mm. The round steel shank with a diameter of Ø25 mm and a length of 250 mm ensures stable cutting even at greater tool overhang. The geometry with an entering angle of 60° allows longitudinal turning with good access to the machined surface.
In the combination clamping system (M), the TNMG 1604rr insert is held simultaneously by a top clamp and a pin in its hole. The negative geometry of the 60° triangular insert with 6 cutting edges is suitable for roughing and medium machining, providing high cutting edge strength and cost efficiency thanks to its double-sided design. The boring bar is compatible with TNMG 16 inserts in various carbide grades — select the grade to match the workpiece material.
Decoding the MT-NR designation of the S25 MT-NR-16 boring bar
What the individual letters in the ISO designation mean
Decoding the designation MT-NR
M
CLAMPING
Combination (M)
The top clamp and pin secure the insert simultaneously
T
INSERT SHAPE
60° triangle 60°
TNMG insert — negative, double-sided, 6 edges (3 per side)
N
ENTERING ANGLE
κr = 60°
Boring bar with a triangular insert set at 60°.
N
CLEARANCE ANGLE
α = 0° (neg.)
Negative geometry — double-sided inserts, edges on both sides
R
DIRECTION
Right-hand (R)
Feed to the left — from the tailstock toward the spindle
Shank: Ø25 mm (S25S, steel) · Insert: TNMG 1604rr
Typical applications of the S25 MT-NR-16 boring bar
Cutting operations:
| ▸ | Longitudinal boring — enlarging and finishing cylindrical bores from Ø32 mm |
| ▸ | Roughing and medium machining of bores — negative TNMG geometry provides a strong cutting edge; for finishing, select an insert with a finishing chip breaker |
| ▸ | Internal taper turning — bearing seats, internal chamfers, Morse tapers |
| ▸ | CNC production runs — repeatable cutting edge positioning and quick insert replacement in the holder |
Included
Package contents for S25 MT-NR-16
Package contents:
| ✓ | Boring bar body S25 MT-NR-16 | 1 pcs |
| ✓ | Combination clamp (clamp + pin) | 1 pcs |
| ✓ | Hex key for insert replacement | 1 pcs |
| ✗ | TNMG 1604rr cutting insert (sold separately) | — |
Compatible TNMG 1604rr insert
TNMG 1604rr
The cutting insert is not included in the set — must be purchased separately. TNMG insert. Negative geometry means that the insert is double-sided and has 6 cutting edges, providing a stronger cutting edge and twice as many edges as a single-sided insert.
Select the insert grade to match the workpiece material: P (structural steels), M (stainless steel), K (cast iron), N (aluminum). You can find compatible inserts in the section "Related products" below.
Insert installation and replacement for the S25 MT-NR-16 boring bar
Instructions for combination clamping (M)
Insert replacement procedure step by step
1 Loosen the clamp
Loosen the clamping screw 2-3 turns
2 Clean the insert seat
Remove chips and debris
3 Install the insert
Fit onto the pin and press down
4 Tighten the clamp
Torque 2.0–3.5 Nm
Important: Do not exceed the recommended tightening torque — this may damage the thread in the seat or crack the insert.
Checks before starting work:
| ▸ | Tool overhang — do not exceed 4×d (100 mm) without support; use vibration damping for greater overhang |
| ▸ | Cutting edge height — set the cutting edge at spindle centerline height |
| ▸ | Insert seat condition — check that the contact surface is not damaged or worn |
| ▸ | Secure clamping — the insert must have no play in the seat |
| ▸ | Indexing — when an edge wears out, rotate the insert to a fresh edge (6 edges in total) |
Note: Use internal coolant (through the spindle) for boring whenever possible. When machining without coolant, reduce cutting parameters by 20–30%. Long tool overhang promotes vibration — if vibration occurs, reduce the depth of cut and increase the feed.
Frequently asked questions — S25 MT-NR-16
The minimum bore diameter is Ø32 mm. In smaller bores, the tool head interferes with the machined wall, preventing proper cutting.
For a steel shank of Ø25 mm, the recommended maximum overhang without damping is 4×d, or 100 mm. Above this value, vibration may occur — reduce the depth of cut or use a vibration-damped boring bar.
The TNMG insert has negative geometry (clearance angle 0°), which means it is double-sided with 6 cutting edges. When one edge wears out, rotate or flip the insert to use the next edge — this significantly reduces tooling cost per part.
Product accessories
Carbide insert TNMG 160408 R-S AE9025 Horn
Reference: 11266 In stock > 10 items
€5.13
€6.31 brutto
BMP5 bushing 3.7x5x13 TNMG 1604 9313 Smoxh
Reference: 14522 In stock > 10 items
€2.11
€2.59 brutto
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Shipping
All orders are delivered by courier company GLS. For orders exceeding 369 PLN gross shipping is FREE
| Courier GLS | Przelew24 / Prepayment | 14,76 zł gross | Delivery time 1 working day |
| Courier GLS | Cash on delivery | 17,26 zł gross | Lead time 1 working day |
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